« MODx Parse Error »

MODx encountered the following error while attempting to parse the requested resource:
« PHP Parse Error »
 
PHP error debug
  Error: Cannot modify header information - headers already sent by (output started at /www/auditpre/www/htdocs/index.php:13) 
  Error type/ Nr.: Warning - 2 
  File: /www/auditpre/www/htdocs/manager/includes/document.parser.class.inc.php 
  Line: 150 
  Line 150 source: header($responseCode);  
 
Parser timing
  MySQL: 0.0135 s(4 Requests)
  PHP: 0.0214 s 
  Total: 0.0349 s